A typical household may have numerous electronic consumer devices that are controlled by remote control devices. A household may, for example, have multiple televisions, set-top boxes, tuners, home theatre systems, CD (compact disc) players, DVD (digital video disc) players, as so forth. Each such electronic consumer device typically is responsive to a different set of operational signals. Accordingly, each electronic consumer device is sold with its own remote control device that transmits appropriate operational signals for controlling the electronic consumer device. The coffee table in front of the television in the typical household can be covered with numerous such remote control devices to control the multitude of electronic consumer devices within the home.
A remote control device called a “universal remote control device” has an ability to output different types of operational signals for controlling different types of electronic consumer devices. When a user presses a key on the universal remote control device (hereafter “universal remote”), the universal remote uses an amount of information called a “codeset” to determine how to generate a corresponding operational signal that is transmitted from the universal remote. Operational signals for each different make and model of electronic consumer device are generated using a different codeset. Operational signals for a first device (for example, a television of a particular make and model) may, for example, be generated using a first codeset whereas operational signals for a second device (for example, a tuner of a particular make an model) may, for example, be generated using a second codeset. If a user wishes to control the first device, then the user first presses a device type key (for example, the “TV” device type key) on the universal remote. Thereafter, operational signals generated by the universal remote are generated using the first codeset. These operational signals control the first device (in this case, the “TV”). If the user then wishes to control the second device, then the user presses another device type key (for example, the “TUNER” device type key) on the universal remote. Thereafter, operational signals generated by the universal remote are generated using the second codeset. These operational signals control the second device (in this case, the tuner).
To program the universal remote to control a desired electronic consumer device, a user generally identifies the make and model of the electronic consumer device in a booklet supplied with the universal remote, finds an associated codeset number listed in the booklet, and then follows procedures to key the codeset number into the universal remote in association with the type of device with which the codeset is to be identified. Thereafter, when a key is pressed on the universal remote, the universal remote uses the identified codeset to generate operational signals. There are now thousands and thousands of various televisions and other types of electronic consumer devices that universal remotes are to be able to control. Nevertheless, universal remotes store many codesets and can accommodate the large number of devices.
Despite the large number of codesets typically stored in universal remotes, it is often desired to be able to control an exotic or unusual or new remote control device for which there is no codeset stored in the universal remote. Consequently, a feature sometimes called a “learning” feature has been incorporated into some universal remotes. The learning feature usually takes advantage of the fact that most remote controls transmit infrared light operational signals. An infrared detector is therefore incorporated into the learning universal remote. This infrared detector senses the infrared operational signal transmitted from another remote control device and converts the infrared operational signal into a photocurrent signal. Circuitry in the learning universal remote analyzes the photocurrent signal, and stores information about the signal. When a user later presses a key on the learning universal remote, the learning universal remote uses the stored information to generate and transmit a facsimile of the learned operational signal. Because the learning remote control device can now generate the operational signals of the other remote control device, the other remote control device is no longer needed. In this way, the learning remote control device can be made to “learn” operational signals from multiple other remote control devices so that the single learning remote control device can then be used in place of the numerous other remote control devices.
FIG. 1 (Prior Art) is a diagram of an infrared operational signal 1 being transmitted from a remote control device 2 to a learning remote control device 3. The infrared operational signal 1 is received by an infrared photodiode 4 of learning remote 3. When infrared operational signal 1 is received by infrared photodiode 4, a reverse photodiode current is made to flow through the photodiode 4. The reverse photodiode current carries the information being conveyed in operational signal 1.
FIG. 2 (Prior Art) is a simplified diagram of the photodiode current in an example of FIG. 1 where the operational signal 1 is mark-space modulated using RECS80 coding. The photocurrent signal includes mark times and space times. During a mark time, the photocurrent pulses on and off at a carrier frequency. The carrier frequency may range, depending on the modulation technique and codeset, from approximately 25 KHz to 500 KHz. In the illustrated example, a digital zero (BIT 0) is encoded as one such mark time followed by two space times. The mark time is an “on-time” and the two space times together form an “off-time”. A digital one (BIT 1) is encoded as a mark time followed by three space times. The mark time is an “on-time” and the three space times together form an “off-time”. The sequence of digital bits is detected in learning remote 3 and constitutes the information carried by operational signal 1.
Electronic consumer device manufacturers often incorporate tuned detector circuits into electronic consumer device to detect such operational signals. The tuned detector circuit in a particular electronic consumer device may be sensitive to only a narrow range of carrier frequencies used by the remote control device supplied along with the electronic consumer device. Consequently, if a learning universal remote is to be capable of learning operational signals encoded using a wide range of different carrier frequencies, then the learning universal remote cannot use a tuned detector circuit. Rather, a detector circuit that is able to detect multiple different carrier frequencies is to be used.
FIG. 3 (Prior Art) is a simplified diagram of a non-tuned infrared photodetector circuit that is used in learning universal remote control device 3. The reverse current 5 flowing through photodiode 4 depends on the intensity of the incoming infrared light of operational signal 1. When the user wishes to teach the learning universal remote device to learn the unknown operational signal, then the learning universal remote device is placed with respect to the remote control device 2 to be learned from as shown in FIG. 1 such that the infrared photodiode 4 of the learning universal remote device 3 can pick up the infrared operational signal 1 transmitted from the remote control device 2 to be learned from. Photocurrent 5 is made to flow through a fifty ohm resistor 6 to convert the photocurrent into a corresponding voltage signal. The voltage signal on node 7 is compared to a fixed reference voltage VREF on node 8. If the magnitude of the photocurrent voltage signal is higher than VREF, then a digital high is output by comparator 9. If the magnitude of the photocurrent voltage signal is lower than VREF, then a digital low is output by comparator 9. Accordingly, each pulse of the carrier frequency modulation signal in the photocurrent signal is detected and is output as a pulse.
From learning attempt to learning attempt, the distance between the two remote control devices 2 and 3 can change. Devices 2 and 3 can be nose-to-nose in which case the infrared energy received by photodiode 4 can be large. Devices 2 and 3 can be several feet apart in which case the infrared energy received by photodiode 4 is small. The variations in infrared signal intensities as received gives rise to a problem. If the infrared transmitter on device 2 is too close to the infrared detector on device 3, then the photodiode 4 may no longer recover to its original dark condition between light pulses. Photocurrent 5 may not decay fast enough because the photodiode is driven into saturation. This saturation is evident as a lower frequency saturation current that is superimposed on higher frequency (carrier frequency) intelligence signal being detected. The intelligence signal, as described above, is modulated at the carrier frequency.
FIG. 4 (Prior Art) is a waveform diagram of a photocurrent voltage signal on node 7 in the detector of FIG. 3 when remote control devices 2 and 3 are too far apart for the learning feature to work properly. The positive peaks of the pulses 10 and 11 of the carrier frequency component of photocurrent 5 are below the reference voltage VREF. The pulses 10 and 11 are therefore not detected by comparator 9.
FIG. 5 (Prior Art) is a waveform diagram of a photocurrent voltage signal on node 7 in the detector of FIG. 3 when remote control devices 2 and 3 are separated by a good distance. The two photocurrent voltage pulses are large and the peaks of the pulses are off the chart. Nonetheless, the photocurrent voltage signal decays to zero voltage between pulses. The points 12-15 at which the photocurrent voltage signal crosses the reference voltage VREF are usable to detect the pulse times of the carrier frequency modulated pulses with adequate precision.
FIG. 6 (Prior Art) is a waveform diagram of a photocurrent voltage signal on node 7 in the detector of FIG. 3. The carrier frequency in the example of FIG. 6 is, however, higher than the carrier frequency in the example of FIGS. 4 and 5. The points at which the photocurrent voltage signal crosses the reference voltage VREF are still usable to detect the pulse times of the carrier frequency modulated pulses.
If the remote control devices 2 and 3 in the higher frequency carrier example of FIG. 6 are, however, brought close together (nose to nose), then the learning remote control device 3 does not properly detect the pulse time of the carrier frequency modulated pulses.
FIG. 7 (Prior Art) illustrates this situation. The intensity of the infrared operational signal 1 as received by photodiode 4 causes photodiode 4 to saturate. This gives rise to a lower frequency saturation current that is superimposed on the carrier frequency component of the photocurrent signal. Due to the low frequency saturation current, the valleys of the photocurrent voltage signal (see FIG. 7) do not return to zero between pulses. Reference voltage VREF is below the envelope of the negative peaks of the photocurrent voltage signal. Comparator 9 therefore does not detect individual carrier frequency pulses. Although the learning feature of the remote 3 may be able to learn the individual bits encoded, remote 3 cannot properly learn the carrier frequency. Because the infrared detector of the electronic consumer device to be controlled is a tuned circuit, just learning the individual bits encoded does not generally enable the regeneration of the operational signal. As explained above, the receiver in the electronic consumer device to be controlled may be tuned so that it only receives operational signals having the proper carrier frequency.
In an attempt to solve the problem of not being able to detect the carrier frequency as illustrated in FIG. 7, conventional learning remote control devices may be supplied with instructions to place the two remotes a certain distance apart. Conventional instructions may also instruct the user to go through a trial and error process at different distances until the learning feature works. These cumbersome techniques are undesirable. An effective and inexpensive solution is desired.